Microtia: Audiology Case #47

The finding here is visible from the doorway, so the interesting work is not spotting it but deciding what it does and does not mean. The right external ear has been small and malformed since birth — no helix, no antihelix, just a rudimentary concha and a lobule — while the left is normal. That is the diagnosis, and it sits on a graded spectrum running from slight diminution of the ear to its complete absence. It is one of the commoner congenital differences of the head and neck, affecting 1.8 to 3.5 per 10,000 births in the United States, one-sided in 77 to 93 percent of cases, right-sided about 60 percent of the time and about two and a half times commoner in boys, all of which this child matches. The part worth getting right is the separation from closure of the ear canal, which is the condition that most often travels with it. The two are genuinely different structures, and here the canal is open and of normal calibre — comfortably wider than 4 mm — with the eardrum visible round its whole circumference, and the scan confirms a normally formed canal, an aerated middle ear and an intact ossicular chain with no atresia plate. That distinction is not academic. A closed or nearly closed canal produces a hearing loss of 40 to 60 dB, close to the ceiling for a purely conductive problem, and it is closure that most often accompanies the two most severe grades of the malformation. His audiogram shows the consequence of having an open canal: thresholds of 5 to 10 dB HL in both ears with no air-bone gap. So the honest answer to his father is that the ear looks different but hears normally, and the classroom seat is a habit rather than a deficit. Two practice points sit underneath this. The good ear was measured rather than assumed, which is the rule for any one-sided problem, and the imaging was deliberately deferred until school age and an actual surgical plan, rather than being done in infancy when it would have added radiation without changing anything.